The present invention relates to a device for engaging a pipe, cable or other elongate article, to facilitate longitudinal displacement of the article.
For example when installing plastic pipes (whether to carry water or gas), it is commonly necessary to displace the pipe longitudinally of itself, for example when drawing it off a reel or passing it through an underground duct. Hitherto, the pipe has been gripped by hand and then pulled or pushed manually in order to displace the pipe longitudinally of itself. However, it is often difficult to maintain an adequate manual grip on the pipe, especially where the outer surface of the pipe is wet or greasy. Similar problems arise when installing plastic-sheathed cables.
We have now devised a device which facilitates the longitudinal displacement of a pipe, cable or other elongate article and which overcomes the problems outlined above.
In accordance with the present invention, as seen from one aspect, there is provided a device for engaging a pipe, cable or other elongate article to displace that article longitudinally, the device comprising a tubular body formed of a plurality of longitudinal parts arranged to be opened apart and then closed together around the elongate article to be displaced, and at least one collar positioned within the tubular body and formed of a plurality of parts carried by respective parts of the tubular body, the collar having a radially inner surface arranged to form an interference engagement with the outer surface of the article to be displaced, and a radially outer surface arranged to engage the inner surface of the tubular body, at least the outer surface of the collar or the inner surface of the tubular body being tapered towards a trailing end of the device.
In use, the longitudinal parts of the tubular body are opened and then engaged around the elongate article to be displaced, such that the inner surface of the collar forms an interference engagement with the surface of that article. The tubular body is then moved longitudinally in a forward direction. This causes the collar to slide towards the trailing end of the tubular body, because of the interference engagement between the collar and the surface of the elongate article around which the device is engaged: this has the effect of wedging the collar firmly against the surface of the pipe. Continued movement of the device therefore displaces the elongate article in the same direction. At the end of a forward stroke of the device, the device may be slid freely back along the article, then another forward stroke executed, and so on until the article has been displaced the required distance: finally, the parts of the tubular body are opened apart to remove the tubular body from the article.
The tubular body may be arranged to receive a single gripping collar. Instead it may be arranged to receive a number of gripping collars, spaced apart along its length: in this case the number of gripping collars which are used, and the positions in which they are placed, may be selected to suit the application. Where the tubular body receives a number of collars, spaced apart along its length, then, in each part of the body, the respective parts of the collars may be joined by a longitudinal spine. The collar parts of each part of the body thus form a unit so that those parts slide as a unit and can be removed and replaced as a unit.
Preferably the or each collar has a radially outer surface which is tapered to match a tapering section of the inner surface of the tubular body in which it is inserted.
Preferably the radially inner surface of the or each collar is formed with a series of annular teeth, preferably directed towards the forward end of the device.
Preferably each part of the collar is formed to a reduced thickness (e.g. by one or more grooves in its inner surface) at a discrete location or at intervals around its circumference, to impart flexibility to it and enable it to adopt a reduced diameter as it is slid, in use, towards the trailing end of the device.
Preferably each of the longitudinal parts of the tubular body is provided with a retaining formation for the respective part of the or each collar. Preferably the collars can be removed and replaced by collars selected to match the diameter of the pipe or other article on which the device is to be used.
Also in accordance with the present invention, as seen from a second aspect, there is provided a device for engaging a pipe, cable or other elongate article to displace that article longitudinally, the device comprising a tubular body formed of a plurality of longitudinal parts arranged to be opened apart then closed together around the elongate article to be displaced, the inner surface of the elongate body being arranged to form an engagement with the outer surface of the article to be displaced.
In use of this device, the longitudinal parts of the tubular body are opened and then closed around the elongate article to be displaced, such that the inner surface of the tubular body engages the outer surface of the elongate article. The longitudinal parts of the tubular body are then held firmly together and the device is moved longitudinally in a forward direction, to displace the elongate article. At the end of a forward stroke of the device, the forces holding the parts of the tubular body together are relaxed, so that the device may be slid back along the article, for another forward stroke to be executed. Preferably the inner surface of the tubular body is formed with a number of annular teeth, preferably directed towards the forward end of the device.
Conveniently, in either of the above-defined devices, the tubular body may comprise two longitudinal parts, although it may instead comprise three or even more longitudinal parts. Preferably the adjacent parts are coupled together so that they can be flexed relative to each other, for opening and closing the tubular body. The longitudinal parts may be formed as one-piece with an integral hinge coupling them together. Preferably the tubular body is made of plastics material by injection moulding.
Either of the above-defined devices may be a hand-held device for manual use. For this purpose, preferably the tubular body has an outer surface for gripping by hand. Preferably a radially-outwardly projecting flange is provided at least at the forward end (and preferably at both ends) of the tubular body, to act as a safety-guard. The tubular body may be relatively short, such that it is gripped by one hand only: alternatively, it may be sufficiently long that it may be gripped by two hands, one behind the other. The parts of the tubular body may be arranged to clip together: a hook may be coupled to one end of the tubular body, to enable it to be towed; in this case, the device may be used for pulling live electric cables, particularly cables up to perhaps 1000 volts rating.
Instead however, either of the above-defined devices may be incorporated in a powered apparatus for the longitudinal displacement of a pipe, cable or other elongate article.
Preferably the trailing end of either of the above-defined devices is formed with an inwardly-directed annular edge for engaging the surface of the article to be displaced. This edge then acts to scrape dirt etc. from the surface of the article as the device is slid in the retracting direction, prior to a forward stroke to displace the article. Instead, this trailing end of the tubular body may be arranged to receive an annular insert (formed in a number of parts which are retained by the respective longitudinal parts of the tubular body), the inner edge of this insert forming a scraping edge. The insert can then be selected of appropriate diameter for the article on which the device is to be used.